A non-contact transmission technology is known in which power or signals are transmitted between electrical apparatuses without requiring direct connection of the electrical apparatuses through wiring. For example, an electronic circuit element (signal isolator) called a “digital isolator” and having electrical isolation function between the input and output for isolating the ground of a logic signal from the ground of an RF signal is known (cf. Patent Literature 1).
A semiconductor driving circuit for driving a high-pressure-resistant switching element such as an insulated gate bipolar transistor (IGBT) has a very high reference potential on the output side of the driving circuit. Therefore, electrical isolation is required between the ground of the input side of the semiconductor driving circuit and the ground of the output side on which the switching element is driven. The non-contact transmission technology is used for such electrical isolation.
For example, as the non-contact transmission technology, electromagnetic resonance couplers (also called “electromagnetic field resonance couplers”) that use the coupling of two electric wiring resonators as disclosed in Patent Literature 4 have been gathering attention in recent years. A feature of the electromagnetic resonance couplers is that highly efficient and long-range signal transmission is possible.